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Date:   Fri, 5 May 2023 12:00:47 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Peng Zhang <zhangpeng.00@bytedance.com>
Cc:     akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        Tad <support@spotco.us>,
        Michael Keyes <mgkeyes@vigovproductions.net>,
        Stable@vger.kernel.org
Subject: Re: [PATCH v2] maple_tree: Make maple state reusable after
 mas_empty_area()
Message-ID: <20230505160047.zn7l4dvvihv2qc2e@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
        Peng Zhang <zhangpeng.00@bytedance.com>, akpm@linux-foundation.org,
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        maple-tree@lists.infradead.org,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        Tad <support@spotco.us>,
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References: <20230505145829.74574-1-zhangpeng.00@bytedance.com>
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* Peng Zhang <zhangpeng.00@bytedance.com> [230505 10:59]:
> Make mas->min and mas->max point to a node range instead of a leaf entry
> range. This allows mas to still be usable after mas_empty_area() returns.
> Users would get unexpected results from other operations on the maple
> state after calling the affected function.
> 
> Reported-by: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
> Reported-by: Tad <support@spotco.us>
> Reported-by: Michael Keyes <mgkeyes@vigovproductions.net>
> Link: https://lore.kernel.org/linux-mm/32f156ba80010fd97dbaf0a0cdfc84366608624d.camel@intel.com/
> Link: https://lore.kernel.org/linux-mm/e6108286ac025c268964a7ead3aab9899f9bc6e9.camel@spotco.us/
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Cc: <Stable@vger.kernel.org>
> Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
>  lib/maple_tree.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 110a36479dced..8ebc43d4cc8c5 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -5317,15 +5317,9 @@ int mas_empty_area(struct ma_state *mas, unsigned long min,
>  
>  	mt = mte_node_type(mas->node);
>  	pivots = ma_pivots(mas_mn(mas), mt);
> -	if (offset)
> -		mas->min = pivots[offset - 1] + 1;
> -
> -	if (offset < mt_pivots[mt])
> -		mas->max = pivots[offset];
> -
> -	if (mas->index < mas->min)
> -		mas->index = mas->min;
> -
> +	min = mas_safe_min(mas, pivots, offset);
> +	if (mas->index < min)
> +		mas->index = min;
>  	mas->last = mas->index + size - 1;
>  	return 0;
>  }
> -- 
> 2.20.1
>